This application has relation to U.S. patent applications Nos. 07/795,989 (filed Nov. 22, 1991), 07/850,283 (filed Mar. 12, 1992), 07/878,469 (filed May 5, 1992), 07/939,600 (filed Sep. 2, 1992), and 07/969,072 (filed Oct. 30, 1992).
1. Field of the Invention
The present invention relates in general to automotive automatic transmissions, and more particularly to a control system for the automotive automatic transmissions.
2. Description of the Prior Art
In order to clarify the task of the present invention, one conventional control system for an automotive automatic transmission will be outlined, which is disclosed in Japanese Patent First Provisional Publication 62-204044.
The control system of the publication proposes a control which is carried out when, during movement of an associated motor vehicle, a shift lever is moved, for example, from Drive (D)-position to Neutral (N)-position and then returned to the D-position. That is, in the control, when a shifting is carried out from D-position to N-position, the gear position having been taken by the transmission at the D-position is memorized, and when thereafter the shift lever is returned to D-position, the memorized gear position is instantly taken by the transmission automatically.
The conventional control system aims to solve undesired select shock which would be produced in such a return shifting and to smoothly restore the vehicle to the former driving condition.
In fact, when the time (which will be referred to as "N-position keeping time" hereinafter) for which the shift lever is kept at N-position is relatively short, satisfied result is obtained from the above-mentioned measure.
However, due to its inherent construction, the conventional control system is forced to show drawbacks when the N-position keeping time is relatively long. In fact, in this case, the shift lever returning to D-position tends to cause uncomfortable select shock and/or useless racing of the associated engine. That is, when the N-position keeping time is long, the possibility in which various factors (such as, vehicle speed, throttle valve angle, etc.,) for determining a suitable gear position of the transmission are subjected to a change tends to increase. Thus, upon the shift lever returning to D-position, it sometimes occurs that the memorized gear position fails to agree with the existing driving condition of the vehicle.